settings.outformat = "pdf";
unitsize(0.5cm);
draw((0, 0){(1, 1)}
         ..{right}(pi / 2, 1)
         ..{(1, -1)}(pi, 0)
         ..{right}(3 * pi / 2, -1)
         ..{(1, 1)}(2 * pi, 0));